using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using static System.Console;
using static System.Math;
using System.Numerics;
using System.Runtime.InteropServices.WindowsRuntime;
//using CS_Contest.Graph;
using CS_Contest.Loop;
using CS_Contest.Utils;
using static Nakov.IO.Cin;
using static CS_Contest.IO.IO;
namespace CS_Contest {
using Li = List<int>;
using LLi = List<List<int>>;
using Ll = List<long>;
using ti3 = Tuple<int, int, int>;
using ti2 = Tuple<int, int>;
internal class Program {
private static void Main(string[] args) {
var sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
SetOut(sw);
new Calc().Solve();
Out.Flush();
}
public class Calc {
public void Solve() {
int n = NextInt(), x = NextInt();
Min(x-1,n-x).WL();
return;
}
}
}
}
namespace Nakov.IO {
using System;
using System.Text;
using System.Globalization;
public static class Cin {
public static string NextToken() {
StringBuilder tokenChars = new StringBuilder();
bool tokenFinished = false;
bool skipWhiteSpaceMode = true;
while (!tokenFinished) {
int nextChar = Console.Read();
if (nextChar == -1) {
tokenFinished = true;
} else {
char ch = (char)nextChar;
if (char.IsWhiteSpace(ch)) {
if (!skipWhiteSpaceMode) {
tokenFinished = true;
if (ch == '\r' && (Environment.NewLine == "\r\n")) {
Console.Read();
}
}
} else {
skipWhiteSpaceMode = false;
tokenChars.Append(ch);
}
}
}
string token = tokenChars.ToString();
return token;
}
public static int NextInt() {
string token = Cin.NextToken();
return int.Parse(token);
}
public static long NextLong() {
string token = Cin.NextToken();
return long.Parse(token);
}
public static double NextDouble(bool acceptAnyDecimalSeparator = true) {
string token = Cin.NextToken();
if (acceptAnyDecimalSeparator) {
token = token.Replace(',', '.');
double result = double.Parse(token, CultureInfo.InvariantCulture);
return result;
} else {
double result = double.Parse(token);
return result;
}
}
public static decimal NextDecimal(bool acceptAnyDecimalSeparator = true) {
string token = Cin.NextToken();
if (acceptAnyDecimalSeparator) {
token = token.Replace(',', '.');
decimal result = decimal.Parse(token, CultureInfo.InvariantCulture);
return result;
} else {
decimal result = decimal.Parse(token);
return result;
}
}
}
}
namespace CS_Contest.Loop {
public static class Loop {
public static void REP(this int n, Action<int> act) {
for (var i = 0; i < n; i++) {
act(i);
}
}
public static void RREP(this int @n, Action<int> act) {
for (var i = n - 1; i >= 0; i--) act(i);
}
public static void REP(this long n, Action<long> act) {
for (var i = 0; i < n; i++) act(i);
}
public static void FOR(this Tuple<int, int, int> t, Action<int> action) {
for (var i = t.Item1; i < t.Item2; i += t.Item3) action(i);
}
public static void FOR(this Tuple<int, int> t, Action<int> action) =>
new Tuple<int, int, int>(t.Item1, t.Item2, 1).FOR(action);
public static void FOR(this Tuple<long, long, long> t, Action<long> action) {
for (var i = t.Item1; i < t.Item2; i += t.Item3) action(i);
}
public static void FOR(this Tuple<long, long> t, Action<long> act) =>
new Tuple<long, long, long>(t.Item1, t.Item2, 1).FOR(act);
public static void ForeachWith<T>(this IEnumerable<T> ie, Action<int, T> act) {
var i = 0;
foreach (var item in ie) {
act(i, item);
i++;
}
}
public static void Foreach<T>(this IEnumerable<T> ie, Action<T> act) {
foreach (var item in ie) {
act(item);
}
}
}
}
namespace CS_Contest.IO {
using Li = List<int>;
using Ll = List<long>;
public static class IO {
public static void WL(this object obj) => WriteLine(obj);
public static void WL(this string obj) => WriteLine(obj);
public static void WL<T>(this IEnumerable<T> list) => list.ToList().ForEach(x => x.WL());
public static Li NextIntList() => ReadLine().Split().Select(int.Parse).ToList();
public static Ll NextLongList() => ReadLine().Split().Select(long.Parse).ToList();
public static T Tee<T>(this T t, Func<T, string> formatter = null) {
if (formatter == null) formatter = arg => arg.ToString();
formatter(t).WL();
return t;
}
public static void JoinWL<T>(this IEnumerable<T> @this, string sp = " ") => @this.StringJoin(sp).WL();
public static void W(this object @this) => Write(@this);
}
}
namespace CS_Contest.Utils {
using Li = List<int>;
using Ll = List<long>;
public static class Utils {
public static List<T> Repeat<T>(Func<int, T> result, int range) =>
Enumerable.Range(0, range).Select(result).ToList();
public static bool Within(int x, int y, int lx, int ly) => !(x < 0 || x >= lx || y < 0 || y >= ly);
public static void Add<T1, T2>(this List<Tuple<T1, T2>> list, T1 t1, T2 t2) => list.Add(new Tuple<T1, T2>(t1, t2));
public static string StringJoin<T>(this IEnumerable<T> l, string separator = "") => string.Join(separator, l);
public static Queue<T> ToQueue<T>(this IEnumerable<T> iEnumerable) {
var rt = new Queue<T>();
foreach (var item in iEnumerable) {
rt.Enqueue(item);
}
return rt;
}
public static void Swap<T>(ref T x, ref T y) {
var tmp = x;
x = y;
y = tmp;
}
public static Dictionary<TKey, int> CountUp<TKey>(this IEnumerable<TKey> l) {
var dic = new Dictionary<TKey, int>();
foreach (var item in l) {
if (dic.ContainsKey(item)) dic[item]++;
else dic.Add(item, 1);
}
return dic;
}
public static int Count<T>(this IEnumerable<T> l, T target) => l.Count(x => x.Equals(target));
public static IEnumerable<T> SkipAt<T>(this IEnumerable<T> @this, int at) {
var enumerable = @this as T[] ?? @this.ToArray();
for (var i = 0; i < enumerable.Count(); i++) {
if (i == at) continue;
yield return enumerable.ElementAt(i);
}
}
}
public class Map<TKey, TValue> : Dictionary<TKey, TValue> {
public Map() : base() { }
public Map(int capacity) : base(capacity) { }
public new TValue this[TKey index] {
get {
TValue v;
return this.TryGetValue(index, out v) ? v : base[index] = default(TValue);
}
set { base[index] = value; }
}
}
public static class MyMath {
public static long GCD(long m, long n) {
long tmp;
if (m < n) { tmp = n; n = m; m = tmp; }
while (m % n != 0) {
tmp = n;
n = m % n;
m = tmp;
}
return n;
}
public static long LCM(long m, long n) => m * (n / GCD(m, n));
public static long ModValue = (long)1e9 + 7;
public static long INF = long.MaxValue;
public static long Mod(long x) => x % ModValue;
public static long DivMod(long x, long y) => Mod(x * ModPow(y, (long)(1e9 + 5)));
public static long[,] CombinationTable(int n) {
var rt = new long[n + 1, n + 1];
for (var i = 0; i <= n; i++) {
for (var j = 0; j <= i; j++) {
if (j == 0 || i == j) rt[i, j] = 1L;
else rt[i, j] = (rt[i - 1, j - 1] + rt[i - 1, j]);
}
}
return rt;
}
public static long ModPow(long x, long n) {
long tmp = 1; while (n != 0) { if (n % 2 == 1) { tmp = Mod(tmp * x); } x = Mod(x * x); n /= 2; }
return tmp;
}
public static bool IsPrime(long n) {
if (n == 2) return true;
if (n < 2 || n % 2 == 0) return false;
var i = 3;
var sq = (long)Sqrt(n);
while (i <= sq) {
if (n % i == 0) return false;
i += 2;
}
return true;
}
public static IEnumerable<int> Primes(int maxnum) {
yield return 2;
yield return 3;
var sieve = new BitArray(maxnum + 1);
int squareroot = (int)Math.Sqrt(maxnum);
for (int i = 2; i <= squareroot; i++) {
if (sieve[i] == false) {
for (int n = i * 2; n <= maxnum; n += i)
sieve[n] = true;
}
for (var n = i * i + 1; n <= maxnum && n < (i + 1) * (i + 1); n++) {
if (!sieve[n])
yield return n;
}
}
}
public static int ManhattanDistance(int x1, int y1, int x2, int y2) => Abs(x2 - x1) + Abs(y2 - y1);
public static T Min<T>(params T[] a) where T : IComparable<T> => a.Min();
public static T Max<T>(params T[] a) where T : IComparable<T> => a.Max();
}
}